NEW YORK — Relatives of Sept. 11 victims bowed their heads in silence Tuesday to mark the moments exactly six years earlier when hijacked planes crashed into the World Trade Center, the Pentagon and a Pennsylvania field.

The dreary skies created a grim backdrop, and a sharp contrast to the clear blue of that morning in 2001.

“That day we felt isolated, but not for long and not from each other,” New York Mayor Michael Bloomberg said as the first ceremony began. “Six years have passed, and our place is still by your side.”

Construction equipment now fills the vast city block where the World Trade Center once stood. The work under way for four new towers forced the ceremony’s move away from the twin towers’ footprints and into a nearby park for the first time.

As people clutched framed photos of their lost loved ones, Kathleen Mullen, whose niece Kathleen Casey died in the attacks, said the park was close enough.

“Just so long as we continue to do something special every year, so you don’t wake up and say, ’Oh, it’s 9/11,” she said.

Lung disease victim added
On this sixth anniversary, presidential politics and the health of ground zero workers loomed, perhaps more than any other.

The firefighters and first responders who helped rescue thousands that day in 2001 and later recovered the dead were to read the victims’ names for the first time. Many of those rescuers are now ill with respiratory problems and cancers themselves, and they blame the illnesses on exposure to the fallen towers’ toxic dust.

For the first time, the name of a victim who survived that towers’ collapse but died five months later of lung disease blamed on the dust she inhaled was added to the official roll.

Felicia Dunn-Jones, an attorney, was working a block from the World Trade Center. She became the 2,974th victim linked to the four crashes of the hijacked airliners in New York, the Pentagon and a field near Shanksville, Pa., where federal investigators say the passengers of United Airlines Flight 93 fought the hijackers on the rallying cry “Let’s roll!”

A memorial honoring Flight 93’s 40 passengers and crew began at 9:45 a.m., shortly before the time the airliner nosedived into the empty field.

“As American citizens, we’re all looking at our heroes,” said Kay Roy, whose sister Colleen Fraser, of Elizabeth, N.J., died when the plane went down.

Homeland Security Secretary Michael Chertoff also spoke to the mourners, telling them: “You have my promise that we will continue to work every single day to protect the people of this country, all in the name of those who perished heroically on Flight 93.”

Presidential politicsIn New York, drums and bagpipes played as an American flag saved from the collapse was carried toward a stage.

Firefighters shared the platform with former Mayor Rudy Giuliani, who many victims’ families and firefighters had said shouldn’t speak at the service to keep from politicizing it.

Giuliani has made his performance after the 2001 terrorist attacks the cornerstone of his presidential campaign, but the Republican has said his desire to be there Tuesday was entirely personal.

“It was a day with no answers, but with an unending line of people who came forward to help one another,” he told those gathered.

After he descended to the trade center site, however, one man yelled “Scum! Scum!” at him, and a woman from the family line said Giuliani didn’t allow enough time for the search for victims’ remains. “Because of Giuliani, we never had closure,” said Sabrina Rivera. Giuliani left without speaking to reporters.

Sen. Hillary Rodham Clinton, seeking the Democratic Party presidential nomination, also attended the ceremonies. Republican Mitt Romney, another presidential contender, issued a statement describing the attacks as the day “radical Islamists brought terror to our shores” and paying tribute to U.S. troops sent to Afghanistan and Iraq in the aftermath.

'A day of recommitment'In Washington, President Bush paused for a moment of silence outside the White House, while Gen. Peter Pace spoke beside the Pentagon wall where one of the hijacked planes broke through.

Pace, chairman of the Joint Chiefs of Staff, told the victims’ families that their loved ones will always be remembered.

“I do not know the proper words to tell you what’s in my heart, what is in our hearts, what your fellow citizens are thinking today. We certainly hope that somehow these observances will help lessen your pain,” he said.

Pace also spoke of the military, calling the anniversary “a day of recommitment.” At the main U.S. base at Afghanistan,
service members bowed their heads
in memory of the victims.

National intelligence director Mike McConnell said U.S. authorities remain vigilant and concerned about “sleeper cells” of would-be terrorists inside the United States. “We’re safer but we’re not safe,” McConnell said on ABC’s “Good Morning America.”

Even though the World Trade Center ceremony gathering was moved out of ground zero, an estimated 3,500 family members descended briefly into the site to lay flowers near the twin towers’ footprints.

Among the first family members down the ramp was Marjorie Miller, whose late husband Joel worked at Marsh & McLennan. She said the rain was almost welcome after five consecutive years of Sept. 11 sunshine.

“A lot of tears coming down from up there,” she said, gesturing toward the sky, “and a lot of tears down here.”

In all, 2,974 victims were killed by the Sept. 11 attacks: 2,750 connected to the World Trade Center, 40 in Pennsylvania and 184 at the Pentagon. Those numbers do not include the 19 hijackers.